<template>
  <div class="spec-preview">
    
    <img :src="(skuImageList[index] || {}).imgUrl" />
    <div class="event" @mousemove="handler"></div>
    <div class="big">
      <img :src="(skuImageList[0] || {}).imgUrl" ref="bigImg" />
    </div>
    <div class="mask" ref="mask"></div>
  </div>
</template>

<script>
import { mapGetters } from "vuex";
export default {
  name: "Zoom",
  data() {
    return {
      index:0
    }
  },

  computed: {
    ...mapGetters(["skuImageList"]),
  },

  methods: {
    handler(event) {
      //获取蒙板元素
      let mask = this.$refs.mask;
      //获取大图
      let bigImg = this.$refs.bigImg;
      //计算出蒙板left与top变化数值
      let x = event.offsetX - mask.offsetWidth / 2;
      let y = event.offsetY - mask.offsetHeight / 2;
      //约束x|y数值范围
      if (x <= 0) x = 0;
      if (x >= mask.offsetWidth) x = mask.offsetWidth;
      if (y <= 0) y = 0;
      if (y >= mask.offsetHeight) y = mask.offsetHeight;
      //动态修改mask元素left与top数值
      mask.style.left = x + "px";
      mask.style.top = y + "px";
      bigImg.style.left = -2 * x + 'px';
      bigImg.style.top = -2 * y + 'px';
    },
  },
  mounted() {
    //通过全局事件总线接受兄弟传递过来的索引数值
    this.$bus.$on('sendIndex',(index)=>{
          //修改自身索引数值
          this.index = index;
    })
  },
};
</script>

<style lang="less">
.spec-preview {
  position: relative;
  width: 400px;
  height: 400px;
  border: 1px solid #ccc;

  img {
    width: 100%;
    height: 100%;
  }

  .event {
    width: 100%;
    height: 100%;
    position: absolute;
    top: 0;
    left: 0;
    z-index: 998;
  }

  .mask {
    width: 50%;
    height: 50%;
    background-color: rgba(0, 255, 0, 0.3);
    position: absolute;
    left: 0;
    top: 0;
    display: none;
  }

  .big {
    width: 100%;
    height: 100%;
    position: absolute;
    top: -1px;
    left: 100%;
    border: 1px solid #aaa;
    overflow: hidden;
    z-index: 998;
    display: none;
    background: white;

    img {
      width: 200%;
      max-width: 200%;
      height: 200%;
      position: absolute;
      left: 0;
      top: 0;
    }
  }

  .event:hover ~ .mask,
  .event:hover ~ .big {
    display: block;
  }
}
</style>
